The inactivation and possible degradation of the bifunctional trpC protein (phosphoribosylanthranilate isomerase-indolegycerol phosphate synthetase) in nongrowing cells of Escherichia coli will be investigated. The amount of the protein in nongrowing cells will be determined by radioactive labeling in vivo and subsequent analysis of crude cell extracts by two-dimensional gel electrophoresis. The kinetic, physical and chemical properties of purified preparations of the protein from nongrowing cells will be studied to test for possible structural alterations in vivo. The inactivation and possible degradation of mutant tryptophan synthetase alpha subunit will be examined in various mutant strains of Escherichia coli containing known amino acid substitutions at specific sites in the alpha subunit. The complementary beta 2 subunit of tryptophan synthestase will also be examined. If in vivo degradation of the trpC protein or one of the mutant alpha subunits occurs, purified preparations of the unstable protein will be used to test for proteolytic activities in crude and fractionated cell extracts. These studies may lead to the identification and characterization of specific E. coli proteases involved in intracellular protein degradation. BIBLIOGRAPHIC REFERENCES: Raymond D. Mosteller, Ruth V. Goldstein and Kaoru R. Nishimoto. "Interactions of Tryptophan Synthetase Subunits in Escherichia coli Containing Mutationally Altered beta2 Subunits". J. Biol. Chem. 252: in press (1977). Raymond D. Mosteller, Kaoru R. Nishimoto and Ruth V. Goldstein. "Instability and Partial Degradation of Phosphoribosylanthranilate isomerase-Indoleglycerol Phosphate Synthetase in Nongrowing Cultures of Escherichia coli. J. Bacteriol. 131: in press (1977).